WASHINGTON (CBS News/CBSDC/AP) — Obama administration officials said a Dallas health care worker who handled a lab specimen from an Ebola-infected man from Liberia who died of the disease is on a Caribbean cruise ship where she has self-quarantined and is being monitored for any signs of infection.

State Department spokeswoman Jen Psaki said in a statement Friday that the woman had shown no signs of the disease and has been asymptomatic for 19 days.

The government is working to return the woman and her husband to the U.S. before the ship completes its cruise. The White House said the State Department was working to secure their transportation home.

The government of Belize reportedly released a statement on Thursday saying it had rejected a U.S. request to allow the cruise passenger to pass through the Philip S.W. Goldson International Airport, which services the Belizean capital.

In the statement, published by a local news network in Belize, the government assured the country’s residents that the passenger “never set foot in Belize.”

“While we remain in close contact with U.S. officials we have maintained the position that when even the smallest doubt remains, we will ensure the health and safety of the Belizean people,” said the statement.

A White House official who was not authorized to be named and requested anonymity said the cruise ship had stopped in Belize but officials there would not allow the passenger to leave the vessel.

Psaki said that when the woman left the U.S. on the cruise ship from Galveston, Texas, on Oct. 12 health officials were requiring only self-monitoring.

An administration official said it’s believed the woman poses no risk but health-care authorities want to get her off the cruise ship and back to the United States out of an abundance of caution.

There have been no restrictions placed on other passengers aboard the ship.

Carnival Cruise Lines said in a statement that the woman, a lab supervisor, remained in isolation “and is not deemed to be a risk to any guests or crew.”

“We are in close contact with the CDC and at this time it has been determined that the appropriate course of action is to simply keep the guest in isolation on board,” the statement said. The CDC is the Centers for Disease Control and Prevention.

Two nurses from the Texas Health Presbyterian Hospital, where the health worker on the cruise also works, have been diagnosed with the deadly virus after working directly with the Liberian man, Thomas Eric Duncan. Duncan died at Texas Health on Oct. 8.

Nurse Nina Pham was transferred late Thursday from Dallas to the National Institutes of Health Clinical Center in Maryland for further treatment, and was said to be in good condition.

Her colleague, Amber Joy Vinson, was transferred earlier in the week to Emory University Hospital in Atlanta.